If you're running a 2D model, then you BC is only 1D... You can do plot->contours and look at a lot of things, but I don't think roughness height is an option... not completely sure though, it might be there. It'll plot the contours for the entire domain, but you can zoom into the BC you're interested in (not sure if that's what you're hoping for though).

If you're running a 3D model, then you can do plot->contours and plot the contours right on your BC.

I am working with the new Beta version of Fluent and there you can import a profile file with the roughness height and constant for specifying the boundary conditions of a wall if you wish. (I try to model flow over a complex terrain with quite a patchy vegetation/roughness pattern.)